JP2002083563A - Scanning electron microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TTL-mode scanning electron microscope capable of giving high resolution to a secondary electron image and effectively providing a reflected electron image with good contrast. SOLUTION: In order not to impair the yield of reflected electrons, the angle of rotation of the reflected electrons by a magnetic field of an objective lens is considered in terms of the energy of reflected electrons, thereby disposing a detector in such a position that the reflected electrons can be captured in as wide an energy range as possible.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning type which scans a sample with an electron beam, detects secondary electrons and reflected electrons generated from a scanning region of the electron beam, and images the shape of the sample surface. The present invention relates to an electron microscope, in which a TTL (Through The Lens) type scanning electron microscope, which obtains a signal with a detector in which secondary electrons and reflected electrons are arranged above an objective lens, is generated on a sample. It is possible to efficiently obtain the information of only the reflected electrons in which the secondary electrons are completely separated, and it is hardly affected by the charging of the sample surface. The present invention relates to a technique for acquiring signals from different directions and enabling three-dimensional observation of minute irregularities on the sample surface.

[0002]

2. Description of the Related Art In a TTL scanning electron microscope, when a voltage that accelerates secondary electrons generated from a sample in the direction of an electron source is not applied to the sample, it is caused by irradiation of a primary electron beam. Secondary electrons with low energy use a Wien filter, which is a velocity separator that combines an electric field and a magnetic field, to bend only the trajectory of the secondary electron without affecting the trajectory of the primary electron. It is possible to directly or indirectly guide the secondary electrons, but by applying a voltage to the sample as in the retarding method,
When generating a steep decelerating electric field between the lower surface of the objective lens and the surface of the sample to decelerate the primary electron beam, the secondary electrons emitted from the surface of the sample are conversely accelerated in the direction of the electron source, It will have a large energy. Therefore, in order to change the trajectory of the secondary electrons in the Wien filter, the voltage and current for generating an electric field and a magnetic field also become large, so that the size of the Wien filter increases and the load on the electric circuit also increases. Not practical for. The same applies to the case of a reflected electron having a large energy, but in such a case, a reflector having an appropriate size with a hole through which the primary electron can pass is provided on the trajectory of the primary electron, and It is performed to collide secondary electrons and reflected electrons with the reflector to generate secondary electrons on the reflector, and to guide the secondary electrons having a smaller energy to a detector with a Wien filter. It is impossible to separate secondary electrons from reflected electrons. For this reason, a blocking voltage applied to the mesh-shaped electrode provided at the sample-side entrance of the Wien filter is applied to the mesh-shaped electrode provided at the sample-side entrance of the Wien filter by decelerating and repulsing secondary electrons coming toward the electron source. Separating secondary electrons from reflected electrons by converting reflected electrons with kinetic energy larger than the potential barrier determined by the potential difference between the applied voltage and the sample into secondary electrons with a reflector, and guiding the electrons to the detector with the Wien filter Is the prior art.

[0003]

As shown in the prior art, in a TTL scanning electron microscope, reflected electrons and secondary electrons are separated by a Wien filter and a blocking voltage, and then the reflected electrons collide with a reflecting plate. In the method in which the secondary electrons generated from the reflection plate are guided to the detector, the solid angle to the primary electron beam irradiation area on the sample viewed from the reflection plate disposed in the filter is not large, and the elevation angle from the sample surface is large. Since only backscattered electrons can be obtained, the efficiency of detecting backscattered electrons is low, and furthermore, only signals having low contrast due to the unevenness of the sample surface can be obtained, and three-dimensional information of the unevenness cannot be obtained. . Therefore, it is an issue to obtain a reflected electron image with high contrast that enables high-resolution observation.

[0004]

A reflected electron is a backscattered electron which is emitted from an electron source and irradiated to a sample by receiving and receiving energy by interaction with a surface of the sample. If it is scattered, the incident energy of the primary electron beam is preserved. On the other hand, the energy of secondary electrons is usually 50 eV or less, which is considerably smaller than that of reflected electrons. First of all, the energy distribution of reflected electrons also depends on the incident energy of the primary electron beam, but elastic scattering peaks and the amount is much smaller than that of secondary electrons. It can be seen that they are broadly distributed in an energy range smaller than the energy of the primary electron beam, and the amount of integrating them over energy is not inferior to that of secondary electrons. Therefore, considering the angle of rotation of the reflected electrons emitted from the sample by the magnetic field of the objective lens with respect to the reflected electrons having different energies, by arranging the detector at a position where the reflected electrons can be captured within a wide energy range as much as possible, The electron yield does not suffer.
Even in a system in which a voltage is applied to a part of a magnetic path including a magnetic pole of the objective lens or a retarding voltage for a primary electron beam is applied to a sample, the energy emitted from the sample surface as in the case of secondary electrons is reduced. When the secondary electrons are small, they are captured by the magnetic field of the objective lens and accelerated in the direction of the electron source by the voltage or retarding voltage applied to a part of the magnetic path. Receive changes. on the other hand,
Reflected electrons have a large output energy from the sample surface,
If the exit elevation angle from the sample surface is small, the velocity component in the direction parallel to the sample surface is large.In the case of reflected electrons, although the electron rotates around the central axis of the magnetic pole due to the magnetic field, the electrons are at an angle close to the exit elevation angle. It is considered that the relative angular distribution of the reflected electrons traveling toward the source and having different scattering angles reflects the exit elevation angle. Therefore, the trajectories of secondary electrons and reflected electrons differ greatly depending on the voltage applied to part of the magnetic path or the application of the retarding voltage. By obliquely arranging the reflected electrons, it is possible to obtain a backscattered electron image substantially free from the mixing of secondary electrons, which can not be obtained by the prior art, and it is possible to capture the backscattered electrons having a small exit elevation angle. The detection efficiency of the reflected electrons is higher than that of the sample, and the unevenness of the sample surface is obtained as an image having a shadow. That is, when the rotation angle of the reflected electrons due to the magnetic field of the objective lens is about 2πn (n is an integer), a bright image is obtained on the side where the detector is arranged, and a dark image is obtained on the opposite side. The second is the emission angle distribution of reflected electrons. As is known as the cosine law, the scattering probability of a primary electron beam that is perpendicularly incident on a sample has a large scattering angle of reflected electrons (the elevation angle from the sample). It will be higher. However, in order to allow the primary electron beam and the secondary electrons to pass through the objective lens, a certain size must be secured and a passage opening must be provided. Have passed,
No detection is possible with the first detector according to claim 2. In order to increase the detection yield of the backscattered electrons, it is necessary to arrange the detector at a position where most of the backscattered electrons scattered at an angle that does not pass through the passage opening can be taken in. Also,
The passage opening has a minimum hole diameter through which secondary electrons can completely pass, and the member having the passage opening is used as a reflector for converting reflected electrons into secondary electrons, and passes through the passage opening. The reflected electrons scattered at an angle not to strike the reflector, and the reflector is made of a material or a structure having a high secondary electron generation rate. Make up for it. However, in a system in which a retarding voltage is applied to the sample in order to ensure a certain level of resolution, applying a voltage that accelerates the primary electron beam to a part of the magnetic path will cause the sample to be reflected even if it is reflected electrons. Since the electron beam is greatly accelerated from the electron source toward the electron source, claim 2. The yield at the described first detector is greatly reduced. Therefore, in the scanning electron microscope of the TTL system using the retarding method, when it is necessary to obtain a reflected electron image, only a voltage that does not impair the yield is applied to a part of the magnetic path. It is necessary to switch the voltage applied to a part of the magnetic path depending on the observation conditions.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention is as shown in FIG. 1, in which a primary electron beam emitted from an electron source (22) by applying a voltage to an extraction electrode (21) by a high voltage power supply (23). (20) passes through the mirror body in a vacuum atmosphere, and is incident on the sample (1) after being converged by the lens system. The scanning electron microscope of the present invention aims at observing even a large diameter wafer of about φ300 mm.
The TL method is adopted. Also, despite the TTL method,
It is necessary to separate the secondary electrons and the reflected electrons to efficiently detect the reflected electrons, and to realize a three-dimensional observation of the observation place by using a plurality of reflected electron detectors. Further, in order to realize high-resolution observation by secondary electrons, a retarding method in which a negative voltage (retarding voltage) is applied to the sample (1) by a high-voltage power supply (2) is adopted. Therefore, the secondary electrons having high energy accelerated in the direction of the electron source by the retarding voltage are guided to the detector by the reflector and the Wien filter as described in [Prior Art]. For reflected electrons generated by backscattering on the sample, a reflector and a detector are arranged by the method described in [Means for Solving the Problems].

In the configuration of the embodiment of the present invention, the shape of the reflector 1 (9) and the arrangement of the backscattered electron detectors 1 (11) and 2 (12) are optimized, and the retarding voltage is constant. The energy (incident energy) of the primary electron beam (20) incident on the sample is determined by the electron source (22) from the retarding voltage of the high-voltage power supply (23) from the primary electron beam (20). By applying a negative voltage obtained by subtracting the voltage of the energy incident on the primary electron beam (20), the trajectory (17) of the secondary electrons emitted from the sample and the reflected electron Control that does not greatly change the yield becomes possible.

From these facts, according to the embodiment of the present invention, the primary electron beam (20) emitted from the electron source (22) is converged by the lens system (28) and becomes a Wien filter E × B. After passing through the filter 2 (19) and the E × B filter 1 (18), X,
It is scanned in the Y direction, passes through the reflector 1 (9), and is finally converged on the sample by the objective lens. The objective lens includes a lower magnetic path (3), an upper magnetic path including an electromagnetic coil for generating a magnetic field (4), a voltage applying magnetic path (5), the voltage applying magnetic path (5) and the upper magnetic path (4). It consists of an insulator (6) for insulation. A positive voltage (hereinafter referred to as a boosting voltage) can be applied to the voltage applying magnetic path (5) by a high-voltage power supply (27), and the primary electron beam (20) is accelerated in the objective lens, and strong excitation is performed. By using the objective lens in the above, it is possible to reduce the aberration of the objective lens and increase the resolution. As means for detecting secondary electrons and reflected electrons generated at the place where the primary electron beam is irradiated on the sample, as described in [Means for Solving the Problems], reflected electrons are generated by the magnetic field of the objective lens. The trajectory of the backscattered electrons in the electromagnetic field analyzed in advance by a computer simulation, such as the backscattered electrons The reflecting plate 1 (9), the backscattered electron detector 1 (11), and the backscattered electron detector 2 (12) are so arranged that a sufficient yield of backscattered electrons can be obtained based on the orbit 1 (7) and the backscattered electron orbit 2 (8). Place it at the optimal position. The backscattered electron detector 1 (1
1) The backscattered electron detector 2 (12) uses a scintillator for converting the energy of the backscattered electrons into light as an electron detector, guides the light generated by the scintillator to a photomultiplier tube by a light guide, and A type that finally outputs the signal from the amplifier that electrically amplifies the output of the tube, but a type that electrically outputs electrons directly from the sample by using a semiconductor detector or a secondary electron multiplier. I do not care.
In this embodiment, two backscattered electron detectors are used and 180
° It is arranged diagonally so as to look at the magnetic poles facing each other,
This position captures reflected electrons emitted from one of the right and left sides of the concave or convex wiring pattern extending in the direction perpendicular to the horizontal (X) scanning direction of the electron beam by one of the two detectors. In addition, the position is set so that a sufficient yield of reflected electrons can be obtained. Since each of the right and left sides of the wiring pattern corresponds to one of the two backscattered electron detectors on a one-to-one basis, the left and right wiring patterns are shaded by switching the backscattered electron detector. A three-dimensional reflected electron image can be obtained. Further, it is possible to detect reflected electrons from multiple directions by using three or more reflected electron detectors, to increase the yield of reflected electrons, and to obtain a three-dimensional reflected electron image.

The reflection plate 1 (9) is connected to the reflected electron orbit 1
The reflected electrons that collide as shown in (7) generate secondary electrons on the reflector 1 (9), and the secondary electrons are reflected by the reflected electron detector 1 (9).
(11) and an electric field by a voltage applied to the scintillator acts on the reflector 1 (9) as detected by the backscattered electron detector 2 (12); The collision surface of the reflected electrons is changed so that the secondary electrons generated by the reflected electrons colliding with 1 (9) collide with the surface of the reflector 1 (9) several times and the number of secondary electrons increases in an avalanche manner. It is processed in a step shape as shown in FIG. Further, as shown in FIGS. 3 and 4, the surface of the reflector 1 (9) is provided with irregularities by sandblasting to obtain the same effect as described above, or the surface of the reflector 1 (9) is plated with gold. As a result, the generation efficiency of secondary electrons due to reflected electrons can be increased, and as a result, the yield of reflected electrons can be increased. In addition to the gold plating, a substance having a high secondary electron generation rate, for example, a beryllium alloy can be plated or vapor-deposited, or can be used as the material of the reflection plate (9) itself. As a characteristic of the shape of the reflector 1 (9), the diameter of the hole through which the electron beam passes is such that the secondary electrons generated in the sample (1) are caused by the retarding voltage as shown in the secondary electron trajectory (17). The secondary electrons are accelerated in the direction of the electron source with a certain degree of spread, but the size of the secondary electrons is the minimum size that can completely pass through, and the reflected electrons emitted from the sample surface at a large elevation angle To the electron source, but the loss is minimized. The other reflected electrons are
After the collision with (9), the reflected electrons are detected by the backscattered electron detector 1 (11) and the backscattered electron detector 2 (12). Three-dimensional observation becomes possible.

After passing through the reflector 1 (9), the secondary electrons pass through the electron beam deflecting means (10) and are provided in the E × B filter 1 (18) and the E × B filter 2 (19). Is converted to low-energy secondary electrons by the reflector,
Secondary electron orbit 1 (15) and secondary electron orbit 2 (16)
Are detected by the secondary electron detector 1 (13) and the secondary electron detector 2 (14). The secondary electron detector 1
(13) and the structure of the secondary electron detector 2 (14) are the reflected electron detector 1 (11) and the reflected electron detector 2 (12).
It is the same as that of

On the other hand, when it is necessary to observe the sample with improved resolution, a positive voltage (boosting voltage) is applied to the voltage application magnetic path (5). In this case, the reflected electrons generated at the position where the primary electron beam is irradiated on the sample are accelerated toward the electron source by the boosting voltage. As described in [Means for Solving the Problems], since the trajectory is no longer the same as the reflected electron trajectory 1 (7) and the reflected electron trajectory 2 (8), the number of electrons colliding with the reflector 1 (9) is also reduced. The yield in the backscattered electron detector 1 (11) and the backscattered electron detector 2 (12) also decreases. Therefore, when performing high-resolution observation or obtaining a backscattered electron image, the boosting voltage should not be applied. Since it cannot be reflected, it is appropriate to perform high-resolution observation with a secondary electron image, and there is no need to obtain a reflected electron image. However, in the embodiment of the present invention, the E × B filter 1 (18) and the E × B filter 2
A mesh-like electrode to which a voltage can be applied is inserted between (19), so that the method of separating reflected electrons and secondary electrons described in [Prior Art] can be performed. Further, since it is necessary to insulate the voltage applying magnetic path (5) from members constituting the magnetic path upper part (4), the coupling with the magnetic path upper part (4) is performed by using an alumina insulator (6). Do through. Therefore, since the voltage applying magnetic path (5) and the upper part of the magnetic path (4) are not integrated as a magnetic material, a magnetic field leaks from a gap between both members. Due to this leakage magnetic field, a magnetic field is also generated on the axis through which the primary electron beam (20) passes. If the on-axis magnetic field has a magnitude that cannot be ignored with respect to the magnetic field intensity generated at the magnetic pole, optimal conditions for the electron optical system cannot be obtained, and therefore, it is necessary to suppress the intensity of the leakage magnetic field. Even with the structure as shown in FIG. 1, the leakage magnetic field is as small as about 1/50 of the on-axis magnetic field at the magnetic pole. However, the structure as shown in FIG. From the projecting portion (50) of the upper part of the voltage applying magnetic path (5) protruding from the part (4), the efficiency of inflow of magnetic flux into the voltage applying magnetic path (5) increases,
The leakage of the leakage magnetic field to the vicinity of the joint of the magnetic path can be reduced, and as a result, the leakage magnetic field on the optical axis can be further reduced to about half. Further, by providing the leakage magnetic field shield (51), the electron beam deflection means (1) is provided.
0) The upper stray magnetic field can also be reduced.

In the embodiment of the invention described above, various characteristic images can be observed, but the backscattered electron detector 1 (1
1), backscattered electron detector 2 (12), secondary electron detector 1
(13) Each detector of the secondary electron detector 2 (14) directly or indirectly detects electrons generated from a sample synchronized with a scanning signal for driving the electron beam deflecting means (10), and after amplification, This signal is converted into an electric signal, and this signal is output to an image display device (26) such as a CRT or a liquid crystal monitor by an image processing device (24). In each detector,
Characteristic signals such as secondary electrons, reflected electrons, energy-separated secondary electrons, and reflected electrons can be obtained, and each detector can be arbitrarily switched by the image display control device (25). As shown in FIG. 5, foreign matter (3
5), the contrast of foreign matter and wiring looks the same in the secondary electron image (32), and the foreign matter appears in the upper wiring layer (3).
When it is difficult to determine whether the detector is located between the layer 3) and the lower wiring layer (34) or on the surface, the detector is a backscattered electron detector (a detector located on the right side of the vertical pattern in FIG. 5). Since the contrast of only the sample surface is enhanced and the upper wiring layer (36) is obtained as a shaded reflected electron image (37), it is possible to determine that a foreign substance exists between the wiring layers. Further, despite the presence of the stain-like foreign matter (41) on the sample surface, there is no difference in contrast with the upper wiring layer (39). If it is difficult to determine whether the detector is located between the lower wiring layer (40) and the lower wiring layer (40), the reflected electron image (42) is set as a backscattered electron detector (a detector located on the right side of the vertical pattern in FIG. ) To detect slight irregularities on the surface and obtain the appearance of a foreign matter (44) in the form of a shaded shade, so that it can be determined that the foreign matter exists on the upper wiring layer (43). Becomes In the embodiment of the present invention, in the backscattered electron detector 1 (11) arranged rightward on the image, the right side and the lower side of the convex side of the observation point on the sample are clear, and the left side and the upper side of the concave side are the same. It becomes clear,
In the backscattered electron detector 2 (12), the left side and the upper side of the convex side of the observation point on the sample are bright, and the right side and the lower side of the concave side are bright, so that the backscattered electron detector 1 (11) and the backscattered electron detector By comparing the images obtained in 2 (12), it is possible to determine the foreign matter and the uneven shape of the wiring pattern. As shown in FIG. 7, in the case of a sample which is easily charged by the irradiated electron beam, the secondary electron image is a secondary electron image (45) in which the observation region reflects the shape and has no contrast.
It may be. In such a case, the reflected electron image (46) is obtained by switching the detector by the image display control device (25), so that the image observation that is hardly affected by the charging of the sample surface can be performed. In the embodiment of the present invention, in the backscattered electron image, as described above, a fine uneven shape is seen as a shadow on the image (a detector located on the right side of the image in FIG. 7). In the secondary electron image, the wiring structure (4
7) also provides contrast due to the difference in structure and composition from the periphery of the wiring structure (47).

In the embodiment of the present invention, as described above, a scintillator is used as the electron detector of the backscattered electron detector, and a positive voltage is applied to the scintillator so that the backscattered electron trajectory 1 (7) The reflected electrons incident from the sample in the orbit such as the electron orbit 2 (8) and the secondary electrons generated in the reflector 1 (9) are drawn into the scintillator and simultaneously accelerated and collide. This drawn electric field slightly leaks into the trajectory of the primary electron beam (20), and there is a possibility that the trajectory of the primary electron beam (20) is bent. It is possible to eliminate the influence on the trajectory of the primary electron beam (20) by adjusting the voltage of one of the left and right backscattered electron detectors and balancing the left and right leaked electric fields. As shown in (1), the reflection plate 1 (9) is placed at the sample side opening of the reflection plate 1 (9).
By providing a metal shield (48) having the same potential as that of the primary electron beam (20), an electrostatic shield is created between the primary electron beam (20) and the scintillator, and the electric field is reliably drawn and the primary electron beam is applied.
(20) It is possible to shield from the orbit. The metal shield (48) is made of a metal mesh (49) as shown in FIG. 10, and has a shielding effect of an electric field and has the reflected electron trajectory 1 (7) and the reflected electron trajectory 2
The reflected electrons entering as shown in (8) pass through the mesh and directly enter the backscattered electron detector, or the reflection plate 1
Collision with (9) generates secondary electrons. Although some backscattered electrons collide with the mesh frame, secondary electrons are generated at the collision point, and these secondary electrons are captured by the electric field from the backscattered electron detector and finally detected by the backscattered electron detector As a result, the yield of reflected electrons is not impaired.

The above is the description of the embodiment of the present invention.

[0014]

In the TTL scanning electron microscope, there is no need to dispose a detector between the objective lens and the sample, so that the working distance can be shortened and the convergence angle of the electron beam can be increased. Therefore, the resolution of the device can be increased. Also, even if a retarding method of applying a voltage to decelerate the electron beam to the sample is employed, reflected electrons and secondary electrons can be separated, and a reflecting plate for converting reflected electrons to secondary electrons is provided. 1. The size and shape of the electron passing holes of the reflector and the magnetic path, and claim 2. By optimizing the arrangement of the first detector described above, a reflected electron image with good contrast can be obtained without impairing the yield of backscattered electrons. Therefore, high-resolution observation is possible as compared with the case where the retarding method is not used, and since there is a margin regarding the resolution, the depth of focus can be increased at the expense of the resolution. In addition, since a voltage set in advance for each observation condition can be applied to the magnetic path, when a reflected electron is required, no voltage is applied to the magnetic path, or even if it is applied, a low voltage is applied. By applying a voltage for accelerating the primary electron beam to the magnetic path, high-resolution observation by secondary electrons becomes possible. Further, claim 2. A secondary electron image and a reflected electron image can be obtained by arbitrarily switching the described detectors, and these images can be synthesized by an image processing device, or a feature amount of each image can be extracted and compared. It is also possible to know the three-dimensional structure of the observation point by using, and from the structure and arrangement of foreign matter and defect parts, it is also possible to obtain information about where there is a problem in the semiconductor device manufacturing process regarding the occurrence of foreign matter and defects It becomes possible.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a scanning electron microscope realizing the present invention.

FIG. 2 is a cross-sectional view of a coupling portion between a magnetic path including a magnetic pole for applying a voltage according to claim 3 and a member forming another objective lens.

FIG. 3 is a sectional view of a member for converting reflected electrons into secondary electrons according to claim 13;

FIG. 4 is a sectional view of a member for converting reflected electrons into secondary electrons according to claim 14;

FIG. 5 is a sectional view of a member for converting reflected electrons into secondary electrons according to claim 15;

FIG. 6 is a schematic diagram of a secondary electron image (left) and a reflected electron image (right) when a foreign substance exists between wiring layers as an effect of the present invention.

FIG. 7 is an effect of the present invention, in which it is difficult to determine whether a thin or stain-like foreign substance is present on the surface or between layers, whereas a reflected electron image (right) is used for the secondary electron image (left). FIG. 9 is a schematic diagram illustrating that three-dimensional observation detects slight irregularities and can determine that a foreign substance is present on the surface.

FIG. 8 shows that the effect of the present invention is to perform three-dimensional observation of the surface structure (here, the cell structure) with reflected electrons when no contrast is obtained in the secondary electron image (left) due to charging of the sample surface. FIG. 4 is a schematic diagram for explaining that a reflected electron image (right) that is hardly affected by charging and whose uneven shape can be determined is obtained.

FIG. 9 is a layout view of the metal shield according to claim 16.

FIG. 10 is a front view and a sectional view of the metal shield according to claim 16;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sample (wafer), 2 ... Negative high voltage power supply, 3 ... Lower magnetic path, 4 ... Upper magnetic path, 5 ... Magnetic path applied, 6 ... Insulator, 7 ... Reflected electron trajectory 1, 8 ... Reflected electrons Tracks 2, 9 ... Reflector plate, 10 ... Electron beam deflecting means, 11 ... Reflected electron detector 1, 12 ... Reflected electron detector 2, 13 ... Secondary electron detector 1, 14 ... Secondary electron detector 2,15 ... Secondary electron orbit 1,
16: secondary electron orbit 2, 17 ... secondary electron orbit, 18 ... E
× B filters 1, 19: E × B filters 2, 20: primary electron beam, 21: extraction electrode, 22: electron source, 23: high voltage power supply for electron gun, 24: image processing device, 25: image display control device .. 26 image display device 27 positive high voltage power supply
Reference numeral 28 denotes a lens system, 29 denotes a step-like step, 30 denotes a sandblast surface, 31 denotes a gold plated surface, 32 denotes an example of a secondary electron image when there is a foreign substance between wiring layers, 33 denotes an upper wiring layer, and 34 denotes a lower wiring. Layers, 35: foreign matter, 36: upper wiring layer, 37: example of reflected electron image when foreign matter exists between wiring layers, 38: example of secondary electron image when stain-like foreign matter exists between wiring layers, 39 ... Upper wiring layer, 40... Lower wiring layer, 41.
... Example of backscattered electron image when stained foreign matter exists between wiring layers
43: upper wiring layer, 44: stained foreign matter having a shadow,
45: an example of a secondary electron image having no contrast due to charging of the sample; 46: an example of a reflected electron image which is not easily affected by the charging of the sample; 47: wiring structure; 48: metal shield; 49: metal mesh , 50: overhang of the magnetic path coupling portion, 51: leakage magnetic field shield.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiro Kubo 882-mo, Oita-shi, Hitachinaka-shi, Ibaraki Prefecture Within the Hitachi Measuring Instruments Group (72) Inventor Naomasa Suzuki 882-mo, Oita-shi, Hitachinaka-shi, Ibaraki, Ltd. 2G001 AA03 BA07 BA15 CA03 GA01 GA06 GA09 GA10 GA13 HA13 JA11 JA13 5C033 DD04 DD09 DE06 NN01 NN02 NP01 NP05 NP06 UU02 UU04 UU05 UU06

Claims (16)

[Claims] 1. A scanning electron microscope in which reflected electrons and secondary electrons are detected by the same or separate detectors. Alternatively, a scanning electron microscope characterized in that a voltage applied to an electrode which is insulated from a magnetic path and disposed on a magnetic pole portion is changed. 2. The method according to claim 1, wherein the primary electron beam emitted from the electron source is expanded.
A lens system for reducing, an electron beam deflecting means for two-dimensionally scanning the primary electron beam to irradiate the sample surface with the electron beam, and a lens for finally converging the primary electron beam on the sample. Passing through an electron beam path opened in the center of the objective lens,
A plurality of detecting means for converting secondary electrons or reflected electrons generated on the sample surface into electric signals, and means for outputting a plurality of signals obtained by the detecting means as images in synchronization with a scanning direction and a scanning speed, respectively Means for controlling the sample irradiation energy of the primary electron beam by a potential difference between the electron source and a voltage applied to the sample; and a voltage applied to a part of a magnetic path including a magnetic pole of the objective lens. And an electron detecting surface is disposed between the electron beam deflecting means and the objective lens, and directly on the electron detecting surface within a solid angle facing the electron beam path of the magnetic pole of the objective lens. One or more first detectors, which are placed at positions containing the trajectories of incident reflected electrons, and which directly take in secondary electrons, or reflected electrons, mainly generated when the reflected electrons collide with the member; It is located above the electron beam deflecting means and mainly In a scanning electron microscope comprising two or more second detectors that directly take in secondary electrons that have passed over the deflecting means or take in secondary electrons generated when the secondary electrons collide with a member, In the case where information of the primary electron beam irradiation area is obtained by obtaining a signal of a secondary electron using the second detector using reflected electrons substantially free from mixing of secondary electrons using the first detector. Does not apply a voltage to a part of a magnetic path including a magnetic pole of the objective lens to which a voltage can be applied, does not require information by reflected electrons, uses the second detector, and mainly uses secondary electrons. When the high resolution observation on the sample surface is performed by detecting the information of the objective lens, in order to reduce the aberration of the primary electron beam due to the objective lens, the primary electron beam is partially provided in a magnetic path including a magnetic pole of the objective lens. Make sure that the energy of the primary electron beam passing through the objective lens is high. A voltage is applied on the sample so that an electric field for accelerating reflected electrons and secondary electrons generated from the sample in the direction of the electron source acts on the sample, and one of the magnetic paths including the magnetic poles of the objective lens is obtained depending on information acquisition conditions. A scanning electron microscope characterized by switching a voltage applied to a part. 3. The scanning electron microscope according to claim 1, wherein a magnetic pole of the objective lens to which a voltage can be applied or a magnetic pole of the objective lens close to the electrode to which a voltage can be applied. The shape of the coupling part is set so that the leakage magnetic field at the coupling part between the magnetic path and the other magnetic path constituting the objective lens does not substantially affect the lens magnetic field due to the lens gap of the objective lens. A scanning electron microscope, comprising: a magnetic field shield member disposed above the coupling portion. 4. The scanning electron microscope according to claim 3, wherein an insulator is inserted into a gap between a magnetic path including a magnetic pole of the objective lens and another magnetic path forming the objective lens. A scanning electron microscope characterized in that: 5. A scanning electron microscope according to claim 2, wherein the irradiation energy of the primary electron beam to the sample is kept constant, the voltage applied to the sample is always constant, and the voltage applied to the electron source is changed. Scanning electron microscope, characterized in that the scanning electron microscope is controlled by: 6. A scanning electron microscope according to claim 5, wherein a voltage is not applied to a part of a magnetic path including a magnetic pole of said objective lens, and a reflected electron signal substantially free of secondary electrons is detected. A scanning electron microscope characterized by obtaining an image that is not easily affected by charging of the sample surface by performing the above. 7. A scanning electron microscope according to claim 5, wherein a voltage is not applied to a part of a magnetic path including a magnetic pole of said objective lens, and switching to the first detector according to claim 2 is performed. A scanning electron microscope characterized in that an uneven shape of a sample surface is obtained as a shaded image by detecting a signal of a reflected electron having substantially no mixing of secondary electrons. 8. A scanning electron microscope according to claim 6, wherein in the case where it is difficult to obtain a contrast of the sample surface shape due to the charging of the sample in the secondary electron image, the reflected electron signal and the secondary electron signal are used on the sample. A scanning electron microscope having a function of confirming the uneven shape of a portion where it is difficult to obtain a contrast of a sample surface shape in a secondary electron image by comparing images of the same portion. 9. A scanning electron microscope according to claim 6, wherein when a semiconductor wafer having a wiring between multilayer films constituting a memory or a logic is used as a sample, the sample is charged by irradiation of primary electrons. If the profile of the wiring above the interlayer is obtained as a secondary electron image and the presence of a defect or foreign matter on the wiring can be confirmed on the secondary electron image, the reflected electron can be arbitrarily switched to the first detector. By acquiring an image, it is possible to selectively observe only information on the sample surface, and by comparing both images, it has a function of distinguishing whether the defect or foreign matter is on the sample surface or between the layers. A scanning electron microscope characterized by the above-mentioned. 10. A scanning electron microscope according to claim 9, wherein a reflection electron detector disposed on the right side with respect to the reference direction when the state in which the orientation flat or the V notch is in front is set as the reference direction of the wafer. A scanning electron microscope capable of judging unevenness of an observation point on a sample by comparing a shaded image with a shaded image obtained by a backscattered electron detector arranged to the left with respect to a reference direction. 11. A scanning electron microscope according to claim 2, wherein the member that collides reflected electrons to generate secondary electrons is metal, and is located below the electron beam deflecting means. Wherein the collision area of the reflected electrons is located below the position of the electron detection surface within a range in which an electric field for capturing the electrons of the first detector acts. microscope. 12. A scanning electron microscope according to claim 11, wherein the member that collides the reflected electrons to generate secondary electrons coincides with the center axis of the magnetic pole of the objective lens and tapers in the direction of the magnetic pole. A scanning electron microscope characterized by a conical shape. 13. A scanning electron microscope according to claim 12, wherein the reflected electron collision region of the member for generating the secondary electrons by colliding the reflected electrons has a stepped circular groove which is symmetric with respect to the central axis of the cone. A scanning electron microscope, wherein the scanning electron microscope is arranged to increase secondary electron generation efficiency. 14. A scanning electron microscope according to claim 12, wherein a reflected electron collision region of a member which collides reflected electrons to generate secondary electrons is formed by treating the surface of said member to form irregularities. A scanning electron microscope wherein electron generation efficiency is enhanced. 15. A scanning electron microscope according to claim 12, wherein a member having a high secondary electron generation rate is a reflected electron collision region of a member that collides reflected electrons to generate secondary electrons. A scanning electron microscope characterized by being plated. 16. The scanning electron microscope according to claim 12, wherein a plurality of leaked electric fields having different intensities from the electron detection surface of the first detector change the trajectory of the primary electron beam. In order to prevent the leaked electric field from leaking into the primary electron beam passage so as not to cause the reflected electron to collide with the tip of a member that generates the secondary electron by colliding the reflected electron, a mesh-shaped member through which the reflected electron can pass. A scanning electron microscope comprising a metal shield.